This application claims the benefit of priority from Japanese Patent Applications No. 2001-084325, filed on Mar. 23, 2001, and No. 2001-275592, filed Sep. 11, 2001. Each of these applications is hereby incorporated by reference in its entirety.
1. Field of the Invention
The invention relates to a magnetic disk drive apparatus having a servo system and methods for writing servo data therein. More particularly, it relates to apparatus and methods for performing self-servo writing based on reference servo data (servo patterns) being preliminarily written in a disk medium.
2. Description of the Related Art
Conventionally, in order to write and read data on and from a target track on a recording surface of a data storage disk medium (hereinafter referred to as a xe2x80x9cdiskxe2x80x9dxe2x80x98), a magnetic disk drive apparatus, such as a hard disk drive apparatus, (hereinafter simply referred to as a xe2x80x9cdisk drivexe2x80x9d) includes a servo system for moving and positioning magnetic head elements onto a target track. The servo system includes a servo controller for controlling a drive on a rotary actuator so as to carry the head elements onto a target track by using reference servo data (servo patterns) on a recording surface of a disk. The reference servo patterns are preliminarily provided at servo areas on a recording surface of a disk at a predetermined interval. The servo controller includes a microprocessor (CPU) for mainly controlling a disk drive and a voice coil motor (VCM) driver for driving a rotary actuator under control of the CPU. The reference servo patterns include track address signals and servo burst signals. Track address signals detect track positions and servo burst signals detect a position in a particular track on the recording surface of a disk.
Conventionally, the reference servo patterns are written in servo areas on each recording surface of a disk by using a specialized instrument for a servo track writer. Thus, there is a need for manufacturing a disk drive that includes a process for writing reference servo patterns on both sides of a disk.
The specialized servo track writer instrument includes a head positioning control system (hereinafter referred to as a xe2x80x9cpositionerxe2x80x9d) in order to drive a rotary actuator in the disk drive before the servo writing process. In order to write servo patterns onto a disk, the disk drive itself is temporarily fixed in the specialized servo writer instrument so as to synchronize each movement of the positioner and a rotary actuator. Thus, the positioner determines a head position by controlling an amount of movement of the rotary actuator as a preceding process for the servo pattern writing operation. The positioner includes a positioning controller for inputting a target position as an absolute position.
The operation for writing servo patterns is performed through a head element of the disk drive. When a target position is inputted, the positioning controller determines an error between a present position of the positioner and a target position. Based on a remaining distance of the target position, the positioning controller calculates an operation amount C(z) for driving a motor in the positioner by a rotation angle M(s). Thus, the positioner is moved by an amount P(s).
The positioner further includes an encoder for measuring a feedback moving amount E(s) of a target position to the positioning controller as an absolute position of the positioner. During the feedback operation, the moving amount E(s) may be affected by noises. The positioner further includes a pushpin that is coupled to a rotary actuator so as to move the actuator by an amount R(s) in accordance with the movement amount P(s). Based on the rotary actuator movement amount R(s), a head slider moves by an amount H(s). Thus, an actual position for writing the servo pattern can be determined. After the servo pattern writing position is determined, there is a possibility for the servo pattern writing position to be influenced by vibrations of a spindle motor (SPM) of the disk drive. The vibrations of the SPM produces an error for the servo pattern writing position.
Further, the servo track writer instrument includes a clock head for writing a clock pattern during a rotation of the disk by the SPM. The servo track writer instrument determines a specific time for writing (writing time) servo pattern along a rotational direction of a disk by reading the clock pattern through the clock head. The servo track writer instrument executes the servo pattern writing operation by using the writing head of the magnetic head element based on the clock timing detected by the clock head. Thus, when the head positioning operation is completed, the servo track writer instrument instructs the writing head to write servo patterns in a target track.
When the servo pattern writing operation for one track circle has completed, the positioner moves to a next position of another target track circle. By repeating the same servo pattern writing operations on succeeding positions on a target track circle, the servo patterns are written on one surface of the disk. Since a disk has two surfaces, the same operation for writing the servo patterns is performed on a second surface of the disk.
In order to accurately write the servo patterns, as explained above, measurements are determined for a relative position between a head position and a disk surface. However, even if the position of the positioner is controlled with high accuracy, it does not mean the relative position error between the head position and the disk surface is reduced since the disk is a rotating body connected to a spindle motor (SPM). Thus, in order to improve the accuracy of the servo pattern writing, there is a need to accurately follow the head position in responding to position variations due to the SPM.
Since the conventional operation for writing servo patterns on a disk is performed by removing a top cover of a disk drive, i.e., both disk surfaces and magnetic head elements are exposed, the servo pattern writing operation must be performed in a clean room environment.
A recent increase of recording density in a disk surface, i.e., a higher track pitch, increases the number of tracks for writing the servo patterns. As a result, an operation time for writing the servo patterns per one disk drive is also increased. So far, it takes more than twenty minutes for writing the servo patterns per one disk drive including a disk that has formed thereon more than ten thousand tracks on one surface. Thus, the servo writer instrument is occupied by one disk drive until completing the servo pattern writing operation on both surfaces of the disk. Therefore, an increase of the track density is expected. Under these circumstances, there is a need to install an increased number of servo writer instruments in an enlarged clean room environment.
When the servo pattern writing operation on both surfaces of a disk have completed, the disk drive is removed from the servo writer instrument, the disk drive is covered with a top cover and is brought to a functional verification process for the disk drive by attaching a circuit board module.
However, the conventional apparatus and methods for writing servo patterns using a specialized servo track writer instrument have serious deficiencies, in particular manufacturing costs and a writing accuracy of the servo patterns.
As explained above, a conventional servo track writer instrument drives a rotary actuator based on movement of the positioner. During driving of the rotary actuator, a relative error between a present position of the positioner and a feedback of a target position is supplied to the position controller as a control amount. As a result, when the positioner reaches a position of a target track, it is assumed that a writing head element on the rotary actuator also reached the position of the target track. Then the position controller calculates an operation amount in order to reduce the relative error between the present position of the positioner and the feedback of the target position. However, the writer instrument essentially needs to seek the relative position between the head element and the disk in order to write the servo patterns with sufficient accuracy. Thus, even if the position of the positioner is controlled with sufficient accuracy, it does not necessarily reduce the error of the relative position between the head element and the disk. Especially since the disk, a rotating device, attached to the SPM, causes position changes. Thus, in order to increase the accuracy for writing the servo patterns, it is expected to correctly follow the head position against the changes of the disk position due to the SPM.
Furthermore, in order to increase the storage density of a disk, a higher track density is required. Thus, the numbers of tracks for writing the servo patterns are also increased. As a result, the servo pattern writing time for a disk drive is also increased. More than one thousand tracks are formed on both surfaces of a disk and it usually takes more than twenty minutes for completing the writing of servo patterns to one whole surface side of a disk. Thus, an increase of the track density is expected.
During the writing of the servo patterns, the servo writer instrument is occupied by one disk drive until completing the writing of the servo patterns on one whole surface side of a disk. Consequently, accompanying the above situation, it is required to increase the production number of the servo writer instrument. Furthermore, the conventional servo writer instrument must be used in a clean room. A site expansion for the clean room environment is also required in connection with the increase of the servo writer instruments, thus, increasing the production number of the disk drive resulting in serious problems. Furthermore, the conventional method for using a servo pattern writer instrument includes the problem of an increase in manufacture cost.
To overcome the above and other disadvantages of the prior art, apparatus and methods consistent with the present invention performs a self-servo writing operation without using a special servo writer in order to increase the accuracy of the write positions and timing of servo patterns and to reduce disk manufacturing costs.
The present invention is intended to overcome the above-mention disadvantages for performing a self-servo writing operations. Embodiments consistent with the present invention may include a magnetic disk drive apparatus that can determine an appropriate servo pattern writing position by measuring a relative position error between a head and a disk surface facing the head.
An embodiment consistent with the present invention relates to a magnetic disk drive apparatus, comprise a disk medium having a disk medium having a first and a second surface, each including a plurality of recording tracks having a certain track width, and at least one of the first and second surfaces of the disk medium including a plurality of preliminarily recorded reference servo data; a first pair of head elements facing close to the first surface of the disk medium for writing a first servo data and/or reading the reference servo data; a second pair of head elements being located symmetrically to the first head element facing close to the second surface of the disk medium for writing a second servo data and/or reading the reference servo data; a head positioner for alternately determining a first and second head position for data writing on the respective surfaces by calculating a first relative position between the second head element and the second surface, based on the reference servo data or the second servo data read by the second head element, and by calculating a second relative position between the first head element and the first surface based on the reference servo data or the first servo data read by the first head element; a head mover for alternately carrying the first or second head element to the data writing position on respective surfaces of the disk medium determined by the head positioner; and a servo data writing controller for controlling the respective servo data writing on the respective data writing positions on the respective surfaces of the disk medium by the respective head element.
Another embodiment consistent with the present invention relates to a magnetic disk drive apparatus, comprising a disk medium including a first and a second data recording surface, at least one of the surfaces of the disk medium having a reference data area in which reference servo data for determining a writing position along a radius direction and reference clock patterns for determining a writing time along a rotational direction are preliminarily recorded; a first and a second pair of magnetic head elements for performing data read/write operations on respective surfaces of the disk medium; and a controller for controlling servo data writing operations in a predetermined area of the respective surfaces by using the reference servo data and the reference clock patterns read by the magnetic head elements facing the respective surfaces during a servo writing operation; wherein the controller includes a positioning controller for determining a writing position of the servo data along a radius direction of the disk medium by using the reference servo data, and a writing controller for determining a writing time of the servo data along a rotational direction of the disk medium by using the reference clock patterns.
A further embodiment consistent with the present invention relates to a method for writing servo data in a magnetic disk drive apparatus including a disk medium having a first and a second surface, each having a plurality of recording tracks and a plurality of preliminarily recorded reference servo data, wherein each of the recording tracks have a track width, a first pair of head elements facing close to the first surface of the disk medium for writing servo data and reading the reference servo data, and a second pair of head elements being located symmetrically to the first head element of the disk medium so as to closely face to the second surface of the disk medium for writing servo data and reading the reference servo data, the method comprising writing a first servo data on the first surface of the disk medium with the first head element; reading the reference servo data or the first written servo data with the first head element; writing a second servo data on the second surface of the disk medium with the second head element; reading the reference servo data or the second written servo data with the second head element; calculating a first relative position between the second head element and the second surface of the disk medium based on the reference servo data or the second servo data read by the second head element; determining the first head position for data writing on the first surface of the disk medium; calculating a second relative position between the first head element and the first surface of the disk medium based on the reference servo data or the first servo data read by the first head element; determining the second head position for data writing on the second surface; and alternately carrying the first or second head element to the determined data writing position on the respective surfaces of the disk medium.
Yet another embodiment consistent with the present invention relates to a method for writing servo data in a magnetic disk drive apparatus including a disk medium having a first and a second data recording surface, each surface having a reference data area in which reference servo data for determining a writing position along a radius direction and reference clock patterns for determining a writing time along a rotational direction are preliminarily recorded and a first and a second pair of magnetic head elements for performing data read/write operations on the respective surfaces of the disk medium; the method comprising reading the reference servo data and the reference clock patterns with a first read head facing the first surface of the disk medium; determining a writing position on the second surface of the disk medium by using the reference servo data read by the first read head; determining a writing time of a second write head by using the reference clock patterns read by the first read head; and writing the reference servo data and the reference clock patterns on the second surface of the disk medium with the second write head.